Rifle control tube



June 18, 1957 A. F. SHAPEL 2,796,005

RIFLE CONTROL TUBE Filed June 7. 1954 INVENTOR.

ALFRED F. SHAPEL ATTORNEYS RIFLE CONTROL TUBE Alfred F. Shape], Boise, Idaho Application June 7, 1954, Serial No. 434,966

1 Claim. (Cl. 8914) The present invention relates to a device for dampening the vibrations of a rifle barrel and for eliminating or reducing the recoil of the rifle.

This application is a continuation-in-part of my prior application Serial No. 197,706, filed November 27, 1950, and now abandoned.

It is now a well known fact that upon firing of a cartridge in a rifle, the barrel immediately begins to vibrate and particularly in a vertical plane. It has been observed by numerous investigators that the forward end of the rifle barrel is initially deflected downwardly at the instant that the bullet emerges from the bore of the rifle. It will readily be understood that even a very slight deflection of the rifle barrel at-that particular instant will result in a very considerable deviation of the bullet from the line of aim. The initial downward deflection of the muzzle of the rifle is followed by a more severe upward deflection after the bullet has emerged from the bore with the net result that the forward end of the barrel tends to climb. This is particularly the case' with automatic rifles firing a continuous burst.

It is also a well known fact that ordinarily a rifle will recoil or kick when fired. This may be physically uncomfortable to the shooter and frequently the expectation of the recoil causes the shooter to flinch as he squeezes the trigger, causing the rifle to deflect from the target. Recoil eliminating devices have been devised heretofore but they have in general been unsatisfactory for the reason that their use caused the rifle to project a loud crack or muzzle blast toward the shooter that was definitely unpleasant.

It is a principal object of the present invention to provide a device which will substantially eliminate the vibration in a rifle barrel upon firing of the rifle.

A further important object of the invention is to provide a device that will reduce substantially the recoil of a rifle.

More particularly it is an object of the present invention to provide a device which will prevent the rifle barrel from raising as the rifle is fired.

A further object is to provide a device to accomplish the foregoing objects without creating an undesirable crack or muzzle blast.

Still another object of the invention is to provide a means for increasing the accuracy of a rifle.

Other objects and advantages of the invention will beom r ppare t i a er- In accordance with the present invention, 1 entrap a portion of the. gases expelled from the rifle bore ahead if. the bullet and derive therefrom a component of force extending in a direction longitudinally of the barrel and apply such component of force to the forward end of the. rifle barrel to place the same intension immediately prior to the time that the bullet leaves the barrel, thereby stabilizing the same and eliminating the tendency for the rifle barrel to deflect out of the line of aim upon firing thereof. The device of the present invention comprises an outer tubular casing attached onto the forward end 2 ,796,005 Patented June 18, 1957 of the rifle barrel and extending forwardly therefrom with an inner tubular member arranged concentrically within the outer tubular member and coaxially of the bore of the rifle barrel, the bore of the inner tubular member being just slightly larger than the bore of the rifle barrel. The two tubular members are spaced radially apart adjacent the rifle muzzle and joined solidly together at their foremost ends. The rear end of the inner tubular member is spaced a slight distance from the end of the rifle barrel, permitting access for the gases expelled from the rifle barrel into the pocket between the inner and outer tubular members, the pocket being vented by a particular arrangement of openings in the upper side of the outer casing.

For a consideration of what is believed novel and inventive, attention is directed to the following description taken in connection with the accompanying drawings, while the features of novelty will be pointed out with greater particularity in the appended claims.

In the drawings:

Fig. 1 is a top plan view illustrating the muzzle control tube constructed in accordance with one modification thereof;

Fig. 2 is a front end view of the device shown in Fig. 1;

Fig. 3 is a longitudinal sectional view taken along the line 3-3 of Fig. 1;

Fig. 4 is a fragmentary detail view illustrating a modification of the present invention; and

Fig. 5 is a fragmentary longitudinal sectional view illustrating another modification of the invention.

Numerous different theories have been propounded heretofore by ballistics experts in attempts at explanation of the muzzle dip phenomena occurring at the instant that the cartridge is fired and prior to the time that the bullet leaves the rifle barrel. Reference is made to the article by F. C. Dyer in The American Rifleman, July 1949, page 35; the text, The American Rifle, by

A Major Townsend Whelen, page 411; and Ideal Handbook No. 36, published by the Lyman Gun Sight Corporation, page 58, and others. For the present purposes, however, it is not necessary to review these technical discussions of muzzle dip phenomena, particularly in view of the fact that the eflicacy of the method and device of the present invention has been definitely ascertained by extensive tests by myself and others conducted under exacting conditions. I have definitely determined that by placing the gun barrel under a relatively heavy tension in the manner herein described, the forward end thereof may be stabilized to such an extent so as substantially to eliminate all tendencies for the muzzle of the barrel to dip immediately following firing of the cartridge and subsequently to climb upwardly.

In accordance with the present invention, I entrap in an elongated chamber open only at the end facing the muzzle a portion of the column of air driven from the rifle bore by the bullet and derive therefrom a component of force extending longitudinally of the gun barrel and in parallel alignment therewith, and apply this component of force onto the forward end of the gun barrel to provide the necessary tensioning thereof.

Referring now to the drawings, the muzzle control device shown therein comprises an outer cylindrical member or shell 10 having forward and rear ends, and upper a nd lower sides. The rear end is conically tapered inwardly and internally threaded as at 11 and is adapted to be threadedly mounted upon the forward end of therifle barrel 12, for which purpose the forward end of the rifle barrel is reduced in diameter so as to provide the shoulder 13 against which the extreme rear end of the tubular member 10 may abut. The tubular member 10 may be locked in place upon the gun barrel by means of a 3 suitable set screw 14 or by other suitable means hereinafter described.

A cylindrical tube 16 having a bore of uniform diameter is mounted within the outer member 10, the forward end portion of the tube 16 being enlarged as indicated at 18 defining a heavy annular shoulder which is threaded externally and cooperatively secured into the threaded forward end of the outer member as indicated at 19. An enlarged annular flange 20 on the tube 16 is adapted to fit snugly against the extreme forward end of the outer member 10. The extreme forward end of the inner tube 16 is conically tapered inwardly as indicated at 21 for appearance and reduction in weight, and, moreover, is provided with a pair of opposed flat faces 22 for engagement by a wrench for facilitating separation of the two tubular members of the device such as for cleaning.

Referring to the sectional view of Fig. 3, particular attention is directed to the fact that the rear end of the inner tubular element 16 is spaced from the forward end of the gun barrel 12 by a distance or gap indicated at 24 and which distance is substantially equal to the diameter of the rifle bore. The outer edges of the rear end of the tubular member 16 are beveled back as indicated at 26 while the uniform internal diameter of the tubular member 16 is only slightly greater than the diameter of the rifle bore so that the bullet may pass freely therethrough without contacting the side walls thereof.

Attention is directed to the fact that an elongated annular space is provided between the outside of the inner cylindrical member 16 and the inside of the outer tubular member 10, which space is closed at the forward end of the device by the enlarged annular shoulder portion 18 of the inner element. provided through the upper wall of the outer member 10, spaced slightly forwardly with respect to the rear end of the tubular element 16, but spaced considerably rearwardly with respect to the forward end of the space between the two member 10 and 16. An elongated annular chamber or pocket 30 is thus formed in the forward end of the device between the inner and outer tubular members constituting a trap for receiving gases expelled from the rifle bore.

It will readily be understood by those skilled in the art that when a cartridge is fired, the column of air ahead of the bullet will be driven forwardly at a high rate of speed and under high compression. Upon emerging from the rifle bore, these gases will expand and a portion of these gases will pass outwardly into the space between the inner and outer tubular elements and be compressed into the pocket 30 in the forward end of the device. While some of these gases will be vented through the openings 32 in the upper end of the device, these openings are relatively small so that the gas is compressed to a very high degree in the pocket 30. The horizontal component of pressure indicated by the arrows 34 is directed against the rear shoulder of the annular portion 18 and this component of force, being in longitudinal alignment with the rifle barrel, imposes a tension thereupon which will effectively dampen the otherwise inherent tendency for the gun barrel to vibrate prior to the time that the bullet leaves the bore.

It is pointed out that there are numerous variable factors involved in the design of the present device, and with particular regard to (l) the spacing between the gun barrel and the adjacent end of the inner tube 16, (2) the volume of the elongated annular pocket or chamber 30, (3) the number, shape and size of the vent openings 32 in the top side of the outer shell 10, and (4) the disposition of the vent openings with respect to the pocket 30 and the rear end of the inner tubular member 16.

With regard to the spacing 24 between the forward end of the gun barrel and the adjacent end of the cylindrical portion 16, it has been determined that, irrespective of variations in the remaining factors, which will be more fully described hereinafter, best results are obtained when this spacing corresponds substantially to the diameter of One or more vent openings 32 are the barrel bore. By decreasing this spacing the passage for the expanding gases into the pocket 30 is restricted to such an extent that the barrel vibrations and recoil of the rifle are not eflectively reduced. On the other hand, if the distance between the rifle muzzle and the inner tube 16 is much greater than the bullet diameter, the bullet will have to jump from the barrel to the tube and may start to yaw. With the preferred spacing the ogive of the bullet will be within the inner tube 16 before the base of the bullet releases from the rifle muzzle, whereby the bullet will tend to remain in stable flight.

As regards the volume of the elongated chamber 30 between the inner and outer tubular members, it should be pointed out that this chamber performs a dual function. The first function, which was briefly mentioned above, is to receive a portion of the gases expelled from the gun barrel by the bullet and to derive therefrom a longitudinal component of force which is applied to the end of the gun barrel to place the same in tension for the purpose of dampening the vibrations thereof and for improving the firing accuracy of the gun. Insofar as this particular function is concerned, it is not necessary that any vent openings, such as 32, be provided in the outer shell. The volume of the elongated annular chamber 30 in such case, that is, between the rear end of the inner tubular member 16 and the opposite end of the chamber 30 adjacent the forward end of the device may correspond in value to the volume of from one to two inches of the length of the bore of the gun barrel. For reasons as will be pointed out more particularly hereinafter, however, it is preferred to provide one or more vent openings 32 in the upper surface of the outer tubular member substantially as shown in the drawings. With such vent openings provided, only the volume of the chamber 30 ahead of the foremost vent opening is considered. Attention is here called to the fact that the radial spacing between the outer surface of the inner tubular member 16 and the inner surface of the outer shell 10 preferably corresponds substantially to one-half the diameter of the gun barrel bore. While this spacing between the concentric tubular memhers is not critical, it will be obvious that it must not be so narrow that the free flow of gases to the extreme forward end of the chamber or pocket 30 is impeded by the resistance thereof. While a chamber volume corresponding to the volume of a one inch length of the gun barrel bore is usually sufiicient for stabilizing the same against undue vibration prior to the time that the bullet leaves the bore, it may be desired to increase the volume of the chamber up to a value corresponding substantially to a two inch length of the gun barrel bore in order to reduce muzzle blast to a desired level with heavy caliber guns such as .45 caliber submachine guns and also in the case of Browning automatic rifles. 1n the case of guns of the latter types which are designed primarily for automatic firing, high accuracy is not so essential and a small degree of accuracy may be sacrificed in order to provide a greater degree of elimination of muzzle blast which is particularly severe with such guns.

The size and arrangement of the vent openings 32 are very important to the most efficient operation of the present device. In the first place it is essential that thevent openings be provided only in the upper surface of the outer shell 10, which is otherwise. solid, particularly around the lower side throughout the full extent thereof. Pref erably the slots are milled at an angle slanting forwardly at a small acute angle a as indicated, which angle may be between about 8 to 15 degrees, but preferably is between 10 to 12 degrees with respect to a plane normal to the longitudinal axis of the device, the reason for which will be explained subsequently. The area of these vent openings is very important to the successful operation of the device and is determined by the area of the inner wall surface of the outer shell 10 defining theouter wall of the annular pocket 30. I have found that most satisfactory results are obtained when the combined area of the vent openings corresponds to about 5% of the inner wall surface of the outer shell between the end of the rifle barrel and the forward end of the pocket 30 between the inner and outer tubular members. With rifles of large caliber and high power it is preferred that two slots be provided as shown. However, with small caliber rifles of low power, such as, for example, a .2 2 long rifle, a single slot or vent opening is sufficient and preferred. Neglecting for the moment the matter of the disposition of the vent openings in the direction longitudinally of the device, their function in the elimination of muzzle jump will now be described. As the explosive gases following the bullet pass outwardly between the muzzle of the gun barrel and the inner end of the inner tube 16 and into the pocket 30, very high pressure is built up within the pocket by these gases, exerting a greater outward, or radial, force against the outer shell in the downward direction than in the upward direction, due to the fact that a part of the wall surface of the upper part of the shell 10 is cut away to form the vent openings. The resultant component of force in the downward direction is sufficient to counterbalance the normal tendency for the front end of the gun barrel to jump upwardly upon release of the explosive gases following the emergence of the bullet from the forward end of the device. It will be obvious that by increasing the size of the vent openings 32 the downward component of force may be increased still more with the net result that the forward end of the gun barrel will actually be kicked in the downward direction by the blast of the explosive gases following the bullet. Through exhaustive tests with many different types of rifles of different calibers and with different powder loads it has been determined that muzzle climb will be substantially eliminated with the size of the vent openings corresponding substantially to 5% of the inner wall area of the outer shell. The size of these vent openings may be diminished below the 5% figure to some value such as 2.5%, but as the size of the vent openings is diminished below 5%, the tendency for the gun muzzle to jump, or climb, reappears to a progressively greater degree. However, even at 2.5% the tendency for the muzzle to climb or jump is still very much less than with the device removed from the gun barrel. If the area of the vent openings is increased greatly over the 5% value mentioned, it has been found that while muzzle climb is eliminated, the muzzle blast increases appreciably. In the fragmentary view of Fig. 4 a single milled slot or vent opening 40 is shown having an effective opening size corresponding to the combined area of the openings 32 as shown in Fig. 1.

Muzzle jump is minimized to such an extent through the use of the present device that the gun can readily be held on the target while shooting and, with a scope on the gun, the hit on the target may be observed. This has not been possible heretofore.

The disposition of the vent openings in the upper surface of the outer shell of the device is of very considerable importance to the proper functioning thereof. The vent openings should be arranged a suflicient distance forwardly of the rear extremity of the tubular portion 16 so that the gases escaping from the end of the gun barrel bore cannot pass outwardly in a direct line through such openings. For example, if the openings were arranged directly opposite the space 24, then the gase expelled from the gun barrel bore ahead of the bullet might escape outwardly therethrough to such an extent as to preclude the development of sufiicient pressure within the chamber formed in the forward end of the device for providing the requisitie degree of tensioning for stabilizing the gun barrel prior to emergence of the bullet from the gun barrel. Moreover, and what is particularly important, the explosive gases following the bullet would discharge directly outwardly through such openings with a sharp muzzle crack or blast. Therefore the edge of the vent opening nearest the muzzle of the gun barrel should be positioned forwardly of the rear extremity of the inner tub ular member 16 by a distance corresponding at least to the diameter of the gun barrel bore. With the vent openings so disposed, the gases emerging from the gun barrel bore must change direction in passing around the rear end of the tubular member 16 before reaching the vent openings. After these gases have changed direction, by virtue of their high velocity they will tend to flow in a straight line to the extreme inner end of the chamber 30 and impinge or be compressed against the inner end wall of such chamber defined by the enlarged shoulder 18. Of course, some of the gases will escape outwardly through the vent openings but not until after they have been cushioned against the volume of entrapped gases in the forward end of the pocket or chamber 30.

It has been mentioned hereinbefore that preferably the slots 32 are milled to face forwardly at an angle of between 10 to 12 degrees. With the slots disposed so that the side walls thereof are vertical to the axis of the rifle barrel or slant rearwardly, it ha been found that objectionable muzzle blast is created. With the slots slanting forwardly as specified, however, it was found that objectionable muzzle blast was entirely eliminated with no apparent decrease in recoil reduction. Whether one or two vent openings are provided in the outer shell, the volume of the pocket 30 ahead of the nearest or foremost edge of the vent openings should be at least, and preferably, equal to the volume of a one inch length of the gun barrel bore, but not greater than the volume of a two inch length of the gun barrel bore. With the vent openings 32 arranged as described, the gun may be fired with a complete absence of muzzle crack such :as usually occurs through the use of conventional muzzle brakes or compensators. Heretofore, in using such other devices, the person firing the gun usually found it necessary to use ear plugs for protection against the discomfort usually caused by muzzle crank but which is entirely unnecessary when using the same gun equipment with the present device. Moreover, upward climb of the barrel is virtually eliminated, making it possible to fire an automatic rifle at bursts of several hundred rounds in rapid succession without any tendency for the barrel to deflect from the line of aim.

As mentioned hereinbefore, the present device is also effective for greatly reducing recoil through elimination of the so-called jet reaction effect. It has now definitely been established by ballistics experts that the greater part of the recoil force arises immediately after the bullet has left the muzzle, due to the escape of high pressure gases forcing the firearm rearwardly. This jet effect is largely nullified through the use of the present device. Due to the relatively long length of the internal cylindrical tube, the bullet passing therethrough functions as a valve core and, during the period of time that the bullet is traversing the length of this bore, the explosive gases are caused to flow outwardly through the restricted space 24 into the pocket 30 between the inner and outer tubular members. The shock wave of the initial blast is cushioned against the gas trapped in the forward end of the pocket 30 while the high pressure is gradually dispersed through the restricted vent opening or openings 32 in the upper side of the outer casing. After the bullet has left the forward end of the bore of the inner tubular member, the initial shock wave and flash are already dispersed and very little flash will be observed after the bullet has left the forward end of the device. In firing a piece of ordnance in close proximity to the ground a cloud of dust is usually blown up, but with the same ordnance piece equipped in accordance with the present invention the dust cloud is completely eliminated. Such a dust cloud frequently made it impossible heretofore to fire in rapid succession on account of poor visibility. With the present device, however, and with the gun fired under the same conditions, little or no dust is stirred up.

An unintended but a very desirable result accompanying the use of the present invention is that rifles equipped with'the device of the invention have increased accuracy. This result has been particularly noticeable in light weight sporting rifles wherein the barrel is of relatively light weight and ordinarily subject to vibration upon firing, so that accuracy and light weight have not been considered compatible. However, even very light weight rifles exhibit good accuracy after providing them with a control tube constructed in accordance with the invention. In one instance, a rifle that previously could not be shot to hold a group less than 8 inches at 100 yards, shot groups of an inch and a half at the same distance after being equipped with the device of the invention.

In the modification as previously described, the rear end of the outer shell 10 is so mounted upon the forward end of the gun barrel as to abut snugly against the shoulder 13. It will be understood that it would be extremely diflicult to thread the end of the gun barrel so that when the muzzle control device of the present invention is screwed tightly in place the vent openings will be sure to face vertically upwardly when the gun is held in the normal firing position. There have been instances where the user in mounting the muzzle control device upon a gun barrel threaded slightly less than the proper amount tried to force the device farther onto the barrel so as to bring the vent openings into the proper upwardly facing position. In so doing the rear end of the outer shell would be forced slightly upwardly onto the shoulder 13 on the gun barrel with the result that the muzzle control device would be thrown out of coaxial alignment with the gun bore. Upon firing, the bullet would drag against one side wall of the bore of the inner tubular member and thus be thrown out of the aimed line of travel. Instead of firmly butting the rear end of the outer shell against the shoulder 13, the device may be locked in place on the gun barrel by means of the set screw 14, but to lock it sufficiently firmly in place solely by means of such a set screw, the threads on the gun barrel would be mutilated by the set screw.

In order to facilitate proper mounting of the muzzle control device upon the gun barrel, I prefer to employ a locking nut arrangement as is more fully illustrated in Fig. 5. As shown in this figure, the gun barrel is threaded over a considerably greater length than is shown in Fig. l and a hexagonal or knurled lock nut 42 is first threaded to the extreme end of the threaded barrel section. The muzzle control device is then screwed in place upon the barrel and into engagement with the lock nut. The device is then backed off a part of a turn from the lock nut until the vent openings face upwardly with the gun barrel held in the proper position for firing. The lock nut is then tightened firmly against the rear end of the muzzle control device and because of full engagement of the lock nut against the annular edge of the outer shell, the muzzle control device will not be thrown out of the desired position of coaxial alignment with the gun barrel bore. In this case, no additional set screw such as 14 will be necessary.

The present device may be constructed for use with l 7 MW%' virtually any rifle following the various guides given above for proportioning the same with respect to the bore of the rifle. 7

Having described the invention in what is considered to be a preferred embodiment thereof, it is desired that it be understood that the specific details described herein are merely for purposes of illustration and that the invention may be'carried out in other ways.

' I claim:

A rifle control tube comprising an outer, cylindrical, tubular member, means for mounting said outer tubular member on the end of a rifle barrel with said outer tubular member extending forwardly of the barrel and coaxially therewith, an inner, cylindrical, tubular member supported concentrically within and spaced from said outer tubular member to define an annular chamber therebetween, the internal diameter of said inner member being uniform and only slightly greater than the internal diameter of the bore of the rifle barrel with which the control tube is to be associated, cooperative means on the forward ends of said members for securing the same together and defining an annular forward wall for said chamber, said inner member being adapted to be spaced from the end of the rifle barrel to which the device is designed to be attached by a distance substantially equal to the bore of said rifle barrel to define a gap between said barrel'and said inner tubular member, said outer member having a vent slot in the top thereof spaced forwardly of the rearward end of said inner tubular member a distance substantially equal to said rifle bore and extending transversely of the outer member, the Walls of said vent slot slanting upwardly and forwardly of the outer member at an angle of between about 8 and 15 degrees with respect to a plane normal to the axis of said outer member, said forward wall being spaced forwardly of said vent slot by such distance that the volume of the chamber between said vent slot and said forward wall is at least equal to the volume of a one inch length of the rifle bore but not substantially greater than the volume of a two inch length of the rifle bore, and the area of said vent slot being approximately five percent of the area of the internal wall surface of said outer member between the end of the barrel and the forward end of the space between said members.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES POWer PAC (published by E. B. Powell, copyright 1948, 48 pages, 2 pages of inside covers). 

